1. General Nature of the Invention
This invention relates to fuel-cell batteries. More particularly, it relates to a battery unit containing a number of fuel-cell blocks, each of which comprises a number of fuel-cells. It also relates to fuel-cell batteries composed of such battery units and to a method for the electrochemical combustion of a fuel in such a battery unit.
2. Description of the Prior Art
A fuel-cell battery is, for practical reasons, frequently subdivided into a number of battery units containing a number of fuel-cell blocks each of which is provided with duct means for the supply and removal of fuel, oxidising agent and, if necessary, also electrolyte.
A plurality of such battery units with auxiliary equipment such as, for example, a pump together, form a fuel-cell battery.
In practice such batteries are frequently used for the electrochemical combustion of hydrogen with the aid of molecular oxygen present in the air. In this process it it possible to use an electrolyte in the form of a solution in water of, for example a base, e.g. KOH.
With such batteries a number of problems are encountered which have hitherto hampered their use on a large scale. A particular problem is presented by the exchangeability of the various component parts of the battery. It has to be possible to replace in a simple manner in situ both the individual battery units and the fuel-cell blocks, which together form the battery unit.
Owing to the pressure-build-up across the blocks it is necessary to take special constructional measures, often at the expence of exchangeability. In order to solve the problem of pressure-build-up in the cell it has previously been proposed to place a number of fuel-cells or fuel-cell blocks one on top of each other and to clamp them together to form a single whole by means of heavy bolts and nuts. A construction of this kind, sometimes called a filterpress stack, is described for example in U.S. Pat. No. 3,099,587. With such a construction it is very difficult to remove a defective cell because the entire battery has then to be dismantled. In addition, such constructions have the characteristic that fairly powerful parasitic currents can occur when a liquid electrolyte is used. These currents are caused by the fact that electrical contact can be made through the electrolyte between the electrodes at different potentials in different fuel-cells, with the consequence that high fuel consumption occurs, while the voltage delivered by the cell may be considerably smaller than is theoretically possible. The result of the latter is that for a given power more powerful currents will occur, so that the electrical measuring and control equipment has to satisfy exacting requirements.